Fix: avoiding issue with PytestUnraisableExceptionWarning

[advance512]

Pull Request check-list

Please make sure to review and check all of these items:

• Does $ tox pass with this change (including linting)?
• Does travis tests pass with this change (enable it first in your forked repo and wait for the travis build to finish)?
• Is the new or changed code fully tested?
• Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?

Description of change

Fix: avoiding issue with PytestUnraisableExceptionWarning that is raised because of __del__() calling self.close() in Redis class, as the self.connection attribute was not set due to early failure in the Redis() constructor.

Example, without this fix:

redis = redis.StrictRedis(**connectionInfo)

in a test for redlock-py, you get this warning due to an unraisable exception:

=============================== warnings summary ===============================
tests/test_redlock.py::TestRedlock::test_bad_connection_info
  /home/user/redlock-py/.venv/lib/python3.8/site-packages/_pytest/unraisableexception.py:78: PytestUnraisableExceptionWarning: Exception ignored in: <function Redis.__del__ at 0x7fd05a194820>
  
  Traceback (most recent call last):
    File "/home/user/redlock-py/.venv/lib/python3.8/site-packages/redis/client.py", line 885, in __del__
      self.close()
    File "/home/user/redlock-py/.venv/lib/python3.8/site-packages/redis/client.py", line 888, in close
      conn = self.connection
  AttributeError: 'Redis' object has no attribute 'connection'
  
    warnings.warn(pytest.PytestUnraisableExceptionWarning(msg))

-- Docs: https://docs.pytest.org/en/stable/warnings.html
========================= 6 passed, 1 warning in 0.65s =========================

[github-actions]

This pull request is marked stale. It will be closed in 30 days if it is not updated.

[chayim]

@dvora-h can you check if this is still valid?

[codecov-commenter]

Codecov Report

Merging #1458 (f4fff1c) into master (8d949a3) will increase coverage by 0.00%.
The diff coverage is 50.00%.

@@           Coverage Diff           @@
##           master    #1458   +/-   ##
=======================================
  Coverage   92.17%   92.17%           
=======================================
  Files         100      100           
  Lines       21024    21026    +2     
=======================================
+ Hits        19378    19381    +3     
+ Misses       1646     1645    -1     

Impacted Files	Coverage Δ
redis/client.py	89.30% <50.00%> (-0.09%)	⬇️
tests/test_cluster.py	98.42% <0.00%> (+0.12%)	⬆️

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[dvora-h]

More than a year ... but yes, it's still valid and we can merge it